Heretofore, the major portion of all plastic snap fasteners were secured or sealed to a substrate or supporting material on their bottom surfaces with their stud or socket members projecting upwardly. Thus, the snap fastener was entirely on one side of the material. An example of this type of fastener is shown in FIG. 35 of U.S. Pat. No. 3,049,462 issued to N. M. Barlow et al on Aug. 14, 1962. The Barlow et al patent also discloses an apparatus for attaching such snap fasteners to the supporting material.
Snap fasteners which penetrate the supporting material are usually made of metals such as those shown in U.S. Pat. No. 3,192,200 issued to D. J. Dadddona, Jr. on July 20, 1965; but, recently plastic snap fasteners which are adapted to penetrate the supporting material and be secured therein have been developed. Representative of the latter type of snap fastener is the type shown in U.S. Pat. No. 3,553,796 issued to A. E. Carlile on Jan. 12, 1971.
The first mentioned snap fasteners which are secured entirely on one side of the material by adhesive or by a heat seal too often are easily pulled off or removed from the supporting material. Accordingly, it is an object of the present invention to provide a method and apparatus for securely sealing snap fasteners to their supporting material.
The second mentioned snap fasteners which must penetrate the material suffer from the disadvantage that the snap fastener is usually composed of at least four separate elements and, in some events, as many as five penetrations of the supporting film is necessary. Applying these fasteners to the supporting film is not only slow but the many penetrations of the supporting film tend to readily initiate tears. Accordingly, it is another object of the present invention to secure a snap fastener to film-like material with only one penetration of the film.
It is a still further object of the present invention to provide a method and apparatus to speedily and automatically apply thermoplastic snap fasteners to thermoplastic film material. The aforementioned and other objects and advantages of the present invention will become obvious to those skilled in the art from the following Summary of the Invention, Drawings, and Description of the Preferred Embodiment.